The goal of our studies is to achieve further progress in the areas of allogeneic and autologous bone marrow transplantation for the leukemias which would result in improved disease-free survival and cure rates by: a) decreasing the leukemic relapse rate following marrow grafting; b) reducing the incidence of acute and chronic graft-versus-host disease; and c) preventing the development of cytomegalovirus associated interstitial pneumonia. To this end, we propose to perform seven clinical trials in this project on "Marrow Grafting for the Leukemias." The five studies proposed for years 04 - 08 are phase III trials which will be carried out jointly at Stanford University Hospital and the City of Hope National Medical Center. In the past, these two institutions have collaborated closely in Medical Center. In the past, these two institutions have collaborated closely in clinical trials which have yielded promising results. Our hypothesis is that our regimens may lead to results which are superior to those attained with other widely utilized approaches. It is the intent of the proposed prospective comparative trials to define the role of the regimens developed by the investigators from the two participating institutions over the last 15 years. In addition, novel techniques will be explored in two clinical trials during years 05-08. These studies have the potential to result in substantial expansion of the scope of bone marrow transplantation and in further improvement in the areas of allogeneic and autologous bone marrow transplantation. The experimental principles for these two trials are based on bone marrow cell fractionation and on positive stem cell selection. These approaches have originated from research which is being performed by investigators of this program project grant. Finally, Project I will serve as the clinical resource for the experimental Projects 3-4 and 8.